/**
 * 获取 blob
 * @param  {String} url 目标文件地址
 * @return {Promise}
 */

function getBlob(url, filename ) {
    return new Promise(resolve => {
        const xhr = new XMLHttpRequest();

        xhr.open('GET', url, true);
        xhr.responseType = 'blob';
        xhr.onload = () => {
            if (xhr.status === 200) {
                resolve(xhr.response);
            }
        };
        xhr.onloadstart = ( progressEvent )=>{

        }
        xhr.onloadend = ( progressEvent )=>{

        }
        xhr.onprogress = ( progressEvent )=>{


        }

        xhr.send();
    });
}

/**
 * 保存
 * @param  {Blob} blob
 * @param  {String} filename 想要保存的文件名称
 */
function saveAs(blob, filename) {
    if (window.navigator.msSaveOrOpenBlob) {
        navigator.msSaveBlob(blob, filename);
    } else {
        const link = document.createElement('a');
        const body = document.querySelector('body');

        link.href = window.URL.createObjectURL(blob);
        link.download = filename;

        // fix Firefox
        link.style.display = 'none';
        body.appendChild(link);

        link.click();
        body.removeChild(link);

        window.URL.revokeObjectURL(link.href);
    }
}

/**
 * 下载
 * @param  {String} url 目标文件地址
 * @param  {String} filename 想要保存的文件名称
 */
function download(url, filename) {
    getBlob(url, filename).then(blob => {
        saveAs(blob, filename);
    });
}

export { download }

//引用示例
// download('http://127.0.0.1:9090/confiles/get/20220829_145722_437b8009047c47d2b672586722ae1759_qczh.png', 'aaa.png');
